Post-Hydration Crosslinking of Ion Exchange Membranes to Control Water Content

Abstract

The utilization of crosslinking as a technique to limit excess water uptake in ion exchange membranes is a well-established approach. However, traditional methods involve performing the crosslinking reaction before the membrane selfsegregates into hydrophilic and hydrophobic domains upon exposure to water. In this study, we employ numerical and molecular simulations to explore the potential of posthydration crosslinking of the polymer at subsaturated conditions. This process allows for the development of a nanosegregated morphology, which establishes well-connected but narrow water channels, while limiting additional sorption of water. The significant reduction in membrane swelling observed in our study indicates that post-hydration crosslinking could be a promising approach to regulate water uptake in ion exchange membranes. Based on our analyses, we propose chemical crosslinking strategies that may yield high membrane gel fractions.

Multistage Condensation Pathway Minimizes Hysteresis in Water Harvesting with Large-Pore Metal–Organic Frameworks

“…The monatomic nature of the model and short-range of the interactions result in over hundred-fold gain in computational efficiency compared to simulations with nonpolarizable all-atom models with long-range electrostatics and orders of magnitude larger gains compared to the many-body polarizable MB-Pol model . The mW model reproduces well the structure and density of liquid water, melting point of ice, and liquid–vapor surface tension of water and has been extensively used for the study of vapor pressures and capillary condensation of water. ,,,− …”

“…Here we develop a computationally efficient united atom (UA) model of a MOF with the pore size and tiling of Co 2 Cl 2 (BTDD) . The UA MOF model is based on short-range interactions and compatible with the monatomic water model mW, which is over 100 times computationally more efficient than the least expensive all-atom models and has been used for the prediction of water sorption isotherms in other porous materials. ,, We use this model MOF to compute and interpret the water sorption and desorption isotherms in Co 2 Cl 2 (BTDD) and MOF variants with tuned hydrophilicity of metal and ligands. Our aim is to elucidate the role of spatial and interaction heterogeneities in the mechanisms and hysteresis of capillary adsorption and desorption in large pore MOFs and to provide molecular guidance for the development of more efficient materials for water harvesting.…”

Tuning Alkaline Anion Exchange Membranes through Crosslinking: A Review of Synthetic Strategies and Property Relationships

“…Generally, crosslinking provides a physical reinforcement mechanism to counteract plasticization effects of water absorption. The introduction of crosslinks prevents polymer rearrangement, mitigating the characteristic exponential water uptake at high hydration conditions [ 69 ]. Significant reductions to both WU and swelling ratios can be realized with even a small equivalence/molar ratios of crosslinkages; representative examples can be found in references [ 51 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 ].…”

Ultraviolet-Activated Solid-State Nitrene Cross-Linking: A Scalable Pathway to Prolonged Lifespan in Anion Exchange Membranes

“…Cross-linked networks exhibit remarkable resistance to the typical exponential rise in water uptake (WU) associated with elevated hydration levels . Effective water management is crucial in the design of AEMs to optimize manufacturability, conductivity, and alkaline stability. , Recent literature on cross-linked AEMs indicates improved performance, − partially attributed to the alleviation of localized dehydration.…”